1. Field of the Invention
This invention relates to an improved grass ski board, and more particularly to an improved roller ski board in which the speed, stemming, sliding and turning is more easily controlled than the known grass roller ski board and compares
Customarily. various grass roller ski boards have been proposed for ski-training on snow free ground. However, the moving peculiarities for sliding, turning, braking, etc., are completely different from the ordinary ski board. due to their inherent length and construction that provided multiple rollers or a caterpillar on the bottom surfaces of the boards. respectively.
In view of such shortcomings in the known grass roller ski board, U.S. Pat. No. 5,096,225, U.S. Pat. No. 5,195,781 and U.S. Pat. No. 5,673,941, have been proposed to simulate the moving peculiarities of the ordinary ski board.
An improved roller ski board disclosed in those roller ski boards, particularly in U.S. Pat. No. 5,673,941, could remarkably improve the moving peculiarities such as for sliding turning or speed and the feel of such movements, in comparison with the ordinary ski board.
However, the known roller ski board has not yet been able to achieve the moving peculiarities like the ordinary ski board, due to the large resistance from the many main rotary rollers pivoting rotatively on the under-surface of the board.
The present roller ski board comprises a board body provided with multiple bearing portions on its undersurface and a plurality of single rollers pivoted rotatively on the bearing portions. The board body also is molded on the whole with the rather small size and an approximate same form as the ordinary ski board, from various single and compound materials having a flexible and repulsive elasticity.
Each single roller comprises a shaft supported firmly on the bearing portion of the roller ski board through a soft material and a single roller body supported rotatively on the shaft with a pair of rotary bearing portions. The pair of rotary bearing portions are molded from an organic material having a lubricative and wearing proof property, as an excellent rotary core material and formed on the whole with the single roller body of soft synthetic resin material to form the single roller.
Each single roller is further arranged along a longitudinal axis of the under-surface of the board at the same distance from their respective both internal lateral side edges.
Each single roller pivots rotatively at a level lower than the bottom-surface of the board so that tangential lines along the lateral outer side edges of each of the rollers do not protrude out from both lines along the lateral side edges of the board body. The body width at a central portion decreases gradually from each of the front and rear edges.
The board body is also formed in a shape of convex curvature slightly curved downwardly from a central portion to the front and rear both edges. Each roller is arranged on the under-surface of the board body and pivots rotatively at a respective position such that each circumference of the rollers contacts along a concave curvature slightly curved upwardly from a horizontal tangent line on running surface of the rollers at the central portion of the board to both the front and rear edges.
On the other side, the board has a plurality of rotative rollers at its central portion consecutive with each pair of rollers at both the front and rear edges. Respectively, which are of a smaller diameter than the rollers at the central portion and separated a little from the central rollers. All peripheries of the rollers are of a concave curvature to reduce the resistance of the board and to prevent an over-turn of the user.
Additionally, the rollers are respectively supported on their respective shafts which are connected firmly on the bearing portion of the board through a bushing set of a soft material having a flexible and elastic property for absorption of vibrations and prevention of shock destruction to the board.
Further, the bearing portions of the board may be provided with slender through-holes, the roller bearings may also be set into the roller bearings or be provided with external circular holes about them; and the roller bodies may be arranged with many blind-holes or through-holes along their outer circular portions to provide a reduced weight for the board and absorption of the stress on the board or from the ground.
Accordingly there is disclosed an embodiment of a roller ski board which is almost of the same form and rather small dimension in comparison with an ordinary ski board and resembles closely with the same in operation.
There is also disclosed a roller ski board which is not only light and strong but also easily operative on a snow free area and has an excellent absorption capacity for shock and vibration as in an ordinary ski board due to the materials and construction of the roller ski board.
There is also disclosed a roller ski board which provides a plurality of rotative single rollers on its under-surface so that each circumference of the rollers contact with a concave curvature slightly curved upwardly to the front and rear edges from a central point of a horizontal tangent line on the under circumference of the rollers in the central portion of the board, to provide a decreased resistance between the roller sliding surface and the ground surface.
There is also disclosed a roller ski board with a plurality of rotative single rollers on it under-surface so that the distance of the internal lateral side edges of each roller arranged on a bearing decreases gradually from both the front and rear edges toward the central portion so as to form two tangent lines at the outer lateral side edges of each pair of the rollers accumulated with or within the lateral side lines of the board, for a smooth sliding and easy turning of the board.
There is also disclosed a grass ski roller board which provides a plurality of rotative single rollers at a central portion of an under-surface of the board consecutively and a respective pair of rollers at the front and rear edges somewhat separated from the central portion for prevention of an overturn of the user.
There is also disclosed a roller ski board which has rotatively a respective pair of smaller rollers that the central rollers at the front and rear edges, and in which all of the rollers are provided with a various uneven pattern on their running surfaces, such as a radial pattern, to provide an excellent edging effect similar to the ordinary ski board.
There is also disclosed a roller ski board which has on its under-surface a plurality of single rollers wherein their vertical sectional surfaces make respectively a small concave curvature slightly curved upwardly on the horizontal tangent line to achieve easily lateral inclination of the board to provide an excellent edging and a smooth operation.
There is also disclosed a roller ski board which has a plurality of single rotative rollers wherein each roller is supported on each shaft connected firmly with each bearing portion of the board through a respective bushing set of soft material to absorb vibration or the shock to the board.
There is also disclosed a roller ski board which has on its under-surface a plurality of rotative single rollers wherein each pair of roller sets into a pair of roller bearings to increase the sliding speed of the board.
There is also disclosed a single roller ski board which has a plurality of rotative roller pairs on its under-surface wherein each pair of rollers has various holes in the roller bodies for reducing weight and providing absorption of all stress to the board.